The Philadelphia Geriatric Center (PGC) - Medical College of Pennsylvania (MCP) Clinical Research Center proposes a program of multidisciplinary research on the psychiatric disorders of the elderly, focusing primarily on those patients who require residential care. The long-term goals of the CRC are: (1) to develop new knowledge on depression, dementia, and the other psychiatric disorders of the aged; (2) to perform research of clinical relevance; (3) to stimulate new research, and (4) to train new scientists in geriatric mental health. The CRC consists of a Core and four laboratories. The functions of the Core include administration of the Center, education, support of the investigations of the laboratories, and the conduct of its own research. The four laboratories are: (1) Laboratory of Health and Affect, directed by Powell Lawton; (2) Laboratory of Psychosocial Processes, directed by Patricia Parmelee; (3) Laboratory of Cognitive Neuroscience, directed by Diana Woodruff-Pak, and (4) Laboratory of Biological Psychiatry, directed by George Simpson and Ira Katz. The Core and each of the Laboratories are described in their own sections. The introduction and overview to the total project presents the goals of the Center, reviews its history and evolution, outlines its structure, and describes its relationship with the parent institutions and with clinical services at PGC.